import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }

    public TreeNode root;

    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
        return A;

    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree(TreeNode root) {
        if (root == null) return null;
        return root;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.println(root + " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    public void inOrder(TreeNode root) {
        if (root == null) return;
        inOrder(root.left);
        System.out.println(root + " ");
        inOrder(root.right);
    }

    // 后序遍历
    public void postOrder(TreeNode root) {
        if (root == null) return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.println(root + " ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    public int size = 0;

    public int size(TreeNode root) {
        if (root == null) return 0;
        size++;
        size(root.left);
        size(root.right);
        return size;
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) return 0;
        return size2(root.left) + size2(root.right) + 1;

    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    public int getLeafNodeCount1(TreeNode root) {
        if (root == null) return 0;
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
        return leafSize;
    }

    /*
     获取叶子节点的个数：子问题
     */
    public int getLeafNodeCount2(TreeNode root) {
        if (root == null) return 0;
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    public int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null) {
            return 0;
        }
        if (k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left, k - 1) + getKLevelNodeCount(root.right, k - 11)
                ;
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    public int getHeight(TreeNode root) {
        if (root == null) return 0;
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);
        return (leftHeight > rightHeight ? leftHeight + 1 : rightHeight + 1);

    }


    // 检测值为value的元素是否存在

    public boolean find(TreeNode root, char val) {
        if (root == null) return false;
        if (root.val == val) {
            return true;
        }
        return find(root.left, val) || find(root.right, val);

    }


    //层序遍历
    public void levelOrder1(TreeNode root) {
        if (root == null) {
            return;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            System.out.print(cur.val + " ");
            if (cur.left != null) {
                queue.offer(cur.left);
            }
            if (cur.right != null) {
                queue.offer(cur.right);
            }
        }




    }


    // 判断一棵树是不是完全二叉树
    public boolean isCompleteTree(TreeNode root) {
        if (root == null) {
            return true;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        boolean end = false; // 标记是否已经遇到了缺失的节点
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if (cur == null) {
                end = true;
            } else {
                if (end) {
                    return false;
                }
                queue.offer(cur.left);
                queue.offer(cur.right);
            }
        }
        return true; // 队列为空且没有违反完全二叉树的规则，所以返回true

    }
}
